A touch panel or touch screen is one of the major interfaces between human and machine, and as a recognition device, can ingeniously combine input and display interfaces, and therefore has the advantages of saving device space and user-friendly operation. Nowadays it has been generally applied to a wide variety of consuming or industrial electronic products. For example, PDAs (Personal Digital Assistant), palm-sized PCs (Personal Computers), tablet computers, mobile phones, handwriting input devices for a smart phone, IAs (Information Appliances), ATMs (Automated Teller Machines) and POS (Points-of-Sale), etc., which can generally be seen in various occasions of business and industry applications.
With the touch panel widely applied in a variety of electronic products, users have more need for the medium and large panel. However, users must hang their wrist and even hang their palm to operate the larger panel. It causes inconvenience and fatigue in use, so users still prefer to use mouse or keyboard as major input interface after the early adopters use touch interface. For avoiding that wrist or palm inadvertently touches the panel, how to effectively determine the signal caused by wrist or palm and to prevent wrist or palm from interfering the detection result is the most important issue in touch technology, so user's wrist or palm can be easily placed on the panel.